1. The Field of the Invention
The present invention relates to a method and apparatus for specifying new values for old parameters for controlling the operation of a mobile device with a network node or element in a network; and, more particularly, relates to a method and apparatus for mapping threshold values to a certain measurable parameter, and coding the threshold values in such a way that one part of the mapping is kept unchanged and another part of the mapping is changed in order to enable different interpretations by the mobile device of the certain measurable parameter, especially for controlling a cell reselection by the mobile device from a Global System for Mobile Communications (GSM) to a Third Generation Partnership Project (3GPP) wireless network.
2. Description of Related Art
In the 3GPP standardization process, a potential problem has been identified in which there may be an insufficient range for a parameter called the “FDD_Qmin parameter” which pertains to handovers between different Radio Access Technologies (RATs), such as Global System for Mobile Communications (GSM) to 3GPP handovers and multimode operation.
In particular, the algorithm controlling the GSM to the Universal Mobile Telecommunications System (UMTS) cell reselection is based on the following formulae:CPICH Ec/No>FDD—QminandCPICH RSCP>RLA(s+n)+FDD—Qoff,where                CPICH Ec/No: Ec/No (received energy per chip) of the CPICH (Common Pilot Channel) of the target 3G Universal Terestrial Radio Access Network (UTRAN) cell,        FDD_Qmin: Minimum threshold for Ec/No for UTRAN frequency division duplex (FDD) cell re-selection,        CPICH RSCP: Received Signal Code Power, average of signal after despreading and combining,        RLA(s+n): Receive Level Average of serving and neighbouring GSM cells, and        FDD_Qoff: Offset between signal strength of GSM and UTRAN Cells.The formulae are derived from the description in 3GPP TS 05.08, sub-clause 6.6.5 of 3GPP TS 05.08, entitled “3rd Generation Partnership Project; Technical Specification Group GSM/EDGE Radio Access Network; Radio subsystem link control (Release 1999)”, which is hereby incorporated by reference in its entirety.        
The FDD_Qmin parameter typically has a range of −20 to −13 dB in 1 dB steps and is coded using 3 bits (see 3GPP TS 05.08 and 3GPP TS 04.18, “3rd Generation Partnership Project; Technical Specification Group GSM/EDGE Radio Access Network; Mobile radio interface layer 3 specification; Radio Resource Control Protocol (Release 1999)”). Some studies suggest that the minimum value of CPICH Ec/No required to maintain a call is approximately −16 to −14.2 dB. If the FDD_Qmin parameter is set to the maximum value of −13 dB, then this only allows a small margin between the FDD_Qmin value and the minimum acceptable CPICH Ec/No threshold. This can result in inter-RAT (Radio Access Technology) cell reselection occurring to the UMTS cell when the cell is not truly suitable and able to offer a reliable, stable service.
FIG. 1 shows drive trial results for the CPICH Ec/No, in which slow fading can be seen and the Ec/No frequently falls below the minimum acceptable level to maintain a call. Thus the FDD_Qmin parameter may need to have a wider range, which would allow a suitable margin between the minimum level and the trigger for inter-RAT cell reselection.
In comparison, the equivalent parameters for controlling UMTS to GSM cell reselection are Qqualmin and SratSearch. The Qualmin parameter has a range of −24 to 0 dB and the SratSearch parameter has a range −32 to +20 dB. The limitation of the FDD_Qmin parameter makes it difficult to achieve stability between 2G and 3G cell reselections. To control inter-RAT reselection ping-pong, a 3G quality threshold must be set for the UTRAN to GSM Edge Radio Access Network (GERAN) cell reselection with a margin of at least 3 dB away from the GERAN to UTRAN cell reselection equivalent.
No effective solutions to this problem are known. In view of this, there is a need in the prior art to solve this problem.